Water recovery system for a cooling tower

ABSTRACT

A water recovery system for a cooling tower includes an intercooler having a first circuit portion and a second circuit portion. The first circuit portion is configured and disposed to receive a liquid desiccant and the second circuit portion is configured and disposed to receive coolant. A flash drum includes an inlet connected to the first circuit portion, a vapor outlet and a liquid desiccant outlet. A condenser is fluidly coupled to the vapor outlet of the flash drum. The condenser includes a condensate outlet. A cooling tower is fluidly connected to the liquid desiccant outlet of the flash drum and the condenser. The cooling tower includes a water stripper having a collector member, and a heat exchanger arranged below the water stripper. The collector member is configured to receive water laden liquid desiccant and the heat exchanger is configured and disposed to receive make-up water from the condenser.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to cooling towers and, moreparticularly, to a water recovery system for a cooling tower.

Turbomachines operate at high pressures. In order to enhance operationin applications such as power generation and mechanical drive gasturbines many turbomachines employ intercoolers that are configured tolower compressed air temperature between compressor stages. Conventionalsystems for lowering the temperature of the compressed air include bothdry and wet cooling systems.

In a dry cooling system, heat is transferred from the extraction airinto cooling water that circulates through heat transfer plates or tubeshaving heat transfer surfaces. After absorbing heat, the cooling wateris passed to a dry cooling tower and guided over additional heattransfer plates or tubes before being re-circulated to cool theextraction air. In a wet cooling system, after absorbing heat from theextraction air, the cooling water is passed to a cooling tower. In thecooling tower, the cooling water is brought into thermally conductivecontact with air. The air extracts heat from the cooling water creatinga plume or vapor. The cooling water is passed back to exchange heat withthe extraction air, and the plume is passed to ambient. In analternative wet cooling system, water is sprayed onto heat transferplates or tubes such as employed in the dry system to further coolclosed loop cooling water. The closed loop cooling water is passed backto exchange heat with the extraction air and the plume is passed toambient. Often times, such as in very dry environments or where water isnot in abundance, it is desirable to extract water from the plume.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a water recovery system for acooling tower includes an intercooler member having a first circuitportion and a second circuit portion. The first circuit portion isconfigured and disposed to receive a liquid desiccant and the secondcircuit portion is configured and disposed to receive coolant. A flashdrum includes an inlet fluidly connected to the first circuit portion, avapor outlet and a liquid desiccant outlet. A condenser is fluidlycoupled to the vapor outlet of the flash drum. The condenser includes acondensate outlet. A cooling tower is fluidly connected to the liquiddesiccant outlet of the flash drum and the condenser. The cooling towerincludes a water stripper having a collector member, and a coolerarranged below the water stripper. The collector member is configuredand disposed to receive water laden liquid desiccant and the cooler isconfigured and disposed to receive make-up water from the condenser.

According to another aspect of the invention, a turbomachine systemincludes a first turbomachine section including an extraction outlet, asecond turbomachine section including an extraction inlet fluidlyconnected to the extraction outlet of the first turbomachine section,and a water recovery system operatively connected to the turbomachinesystem. The water recovery system includes an intercooler member havinga first circuit portion and a second circuit portion. The first circuitportion is configured and disposed to receive a liquid desiccant and thesecond circuit portion is configured and disposed to receive coolant.The intercooler member is configured and disposed to remove heat from anextraction fluid passing from the extraction outlet. A flash drumincludes an inlet fluidly connected to the first circuit portion, avapor outlet and a liquid desiccant outlet. A condenser is fluidlycoupled to the vapor outlet of the flash drum. A cooling tower isfluidly connected to the liquid desiccant outlet of the flash drum andthe condenser. The cooling tower includes a water stripper having acollector member, and a cooler arranged below the water stripper. Thecollector member is configured and disposed to receive water ladenliquid desiccant and the cooler is configured and disposed to receivewater from the condenser.

According to yet another aspect of the invention, a method of extractingwater from vapor emitted by a cooling tower includes passing a waterladen liquid desiccant though an intercooler, absorbing heat into thewater laden liquid desiccant forming a heat laden liquid desiccant,directing the heat laden liquid desiccant through a flash drum,extracting water vapor from the heat laden liquid desiccant in the flashdrum forming a substantially water free liquid desiccant, introducingthe substantially water free liquid desiccant into wet air in thecooling tower, absorbing water from the wet air into the substantiallywater free liquid desiccant forming a water laden liquid desiccant, andpassing the water laden liquid desiccant back into the intercooler.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

The FIGURE is a schematic diagram of a turbomachine system including asystem for recovering water from a cooling tower in accordance with anexemplary embodiment.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

As best shown in the FIGURE, a turbomachine system in accordance with anexemplary embodiment is indicated generally at 2. Turbomachine system 2includes a first compressor section 4 operatively connected to a secondcompressor section 6. Second compressor section 6 is fluidly connectedto a turbine section 8 via combustor 10. First and second compressorsections 4 and 6 are operatively connected to turbine section 8 througha common compressor/turbine shaft 12. First compressor section 4includes an inlet 15 that receives air through an intake 16. Firstcompressor section 4 also includes an extraction air outlet 18 thatdelivers extraction air 19 to an extraction air inlet 20 on secondcompressor section 6. Second compressor section 6 is also shown toinclude an outlet 22 that is fluidly connected to combustor 10. Turbinesection 8 is shown to include an inlet 24 that is fluidly connected to acombustor outlet (not separately labeled) and an outlet or exhaust 26that leads to an exhaust stack 30. In accordance with the exemplaryembodiment shown, heat is removed from extraction air 19 prior tointroduction into extraction air inlet 20. The heat is removed by awater recovery system 40, which, as will be discussed more fully below,in addition to recovering water from cooling tower vapor, also lowers atemperature of extraction air flowing between first and secondcompressor sections 4 and 6.

As shown, water recovery system 40 includes a primary or intercooler 44having a first circuit portion 46 and a second circuit portion 48 thatlead to a cooling tower 50 having a water stripper or absorber 52. Waterstripper 52 strips or absorbs moisture contained in the air passingthrough the cooling tower 50. As will be discussed more fully below,first circuit portion 46 is fluidly isolated from second circuit portion48 in intercooler 44. First and second circuit portions 46 and 48 arefluidly connected to cooling tower 50. First circuit portion 46 includesa liquid desiccant that is in a heat exchange relationship withextraction air 19. As will become more readily apparent below, theliquid desiccant is configured to remove moisture from vapor passingfrom cooling tower 50. In accordance with the exemplary embodiment, theliquid desiccant takes the form of aqueous alkali halides, aqueousalkali nitrates, or glycol. Alkali halides include lithium bromide(LiBr), lithium chloride (LiCl), calcium chloride (CaCl₂), zinc chloride(ZnCl₂), zinc bromide (ZnBr) and the like. Alkali nitrates includepotassium nitrate (kNO₃), and lithium nitrate (LiNO₃), and the like.Glycol includes ethylene glycol (C₂H₆O₂) and the like. Of course itshould be understood that the particular type of liquid desiccant couldreadily vary.

First circuit portion 46 leads from intercooler 44 to a flash drum 55.Coolant or water laden liquid desiccant enters an inlet 57 of flash drum55. In flash drum 55, the water from the water laden liquid desiccantflashes or vaporizes leaving behind a concentrated solution orsubstantially water free liquid desiccant. By substantially water free,it should be understood that the liquid desiccant leaving flash drum 55has a water content that is at least 0.4% less than the water content ofthe liquid desiccant entering flash drum 55. The vapor passes from flashdrum 55 through a vapor outlet 60 and the substantially water freeliquid desiccant passes from flash drum 55 through a liquid desiccantoutlet 63.

The substantially water free laden liquid desiccant passed from liquiddesiccant outlet 63 to a heat exchanger 68. Heat exchanger 68 removesheat entrained within the substantially water free liquid desiccant.From heat exchanger 68, the substantially water free liquid desiccant isdirected through a liquid desiccant spray member 71 by a pump 74. Liquiddesiccant spray member 71 distributes the substantially water freeliquid desiccant into wet or humid air flowing upward from cooling tower50. The substantially water free liquid desiccant absorbs moistureentrained in the wet or humid air, transforms into water laden liquiddesiccant, and falls into a liquid desiccant collector 80. A pump 84urges the water laden liquid desiccant back to first circuit 46 ofintercooler 44.

In further accordance with the exemplary embodiment, vapor passing fromflash drum 55 is guided to a condenser 100. The vapor is cooled andtransformed into make-up water. The make-up water is then passed to awater spray member 104 by a pump 106. At this point it should beunderstood that additional make-up water may be supplied to water spraymember 104 via an external water supply conduit 108. The make-up waterfalls or is sprayed upon a secondary heat exchanger or cooler 120.Secondary cooler 120 is used to reject the remaining heat from secondcircuit portion 48 to ambient. In accordance with one aspect of theexemplary embodiment, secondary cooler 120 includes a wicking materialthat is utilized to enhance evaporative performance. In accordance withone aspect of the exemplary embodiment, collection tray 125 is arrangedbelow secondary cooler 120. The collection tray is positioned to catchexcess water passing from secondary cooler 120. A pump (not shown) isfluidly connected to collection tray 125 and operates to recirculate anyrecovered water back to, for example, pump 106. Another pump 130 urgescooling water back to second circuit portion 48 of intercooler 44. Withthis arrangement, water recovery system 40 not only reduces the loss ofwater exiting a cooling tower, but also provides cooling to lowertemperatures of compressor extractions. Of course, it should beunderstood that the intercooler (or equivalent heat exchanger) coupledto a cooling tower could be employed in a wide variety of installationssuch as a steam turbine condenser system but should not be considered asbeing limited to cooling turbomachine extractions.

The exemplary embodiment has advantages over alternative dry coolingsolutions. A conventional dry cooling system would supply hightemperature coolant exiting the intercooler to an air-cooled heatexchanger. The coolant would be cooled in the air-cooled heat exchangerto a required return temperature of the intercooler. Air-cooled heatexchangers designed for this purpose are very large and expensive, inorder to be suitable for ambient conditions that include above normaltemperatures that often provide small temperature differences betweenthe air and the coolant return temperature. In contrast, the exemplaryembodiment permits the air-cooled heat exchanger to be operated athigher exiting temperatures than is possible with conventional drycooling system. For example, exiting temperature of the liquid desiccantair-cooler is about 122° F. (50° C.). This is significantly higher thanthe required intercooler return temperature of about 102° F. (38.9° C.).This added temperature margin or driving force leads to smaller and lessexpensive air-coolers and greater operating margin in hot weather.

An additional advantage of the exemplary embodiment is flexibility inoperating conditions. For example, it is possible to operate the coolingsystem so that liquid desiccant collects nearly all of the water used inthe cooling tower, so that very little makeup water is required. Howeverthe system can be designed to have the flexibility to use more water inthe cooling tower than is collected by the liquid desiccant. Thisoperation may be useful in hot weather as it allows the system to beoptimized for year-round performance, as opposed to be designed for themost challenging conditions.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A water recovery system for a cooling tower, the water recoverysystem comprising: an intercooler member including a first circuitportion and a second circuit portion, the first circuit portionconfigured and disposed to receive a liquid desiccant and the secondcircuit portion being configured and disposed to receive coolant; aflash drum including an inlet fluidly connected to the first circuitportion, a vapor outlet and a liquid desiccant outlet; a condenserfluidly coupled to the vapor outlet of the flash drum, the condenserincluding a condensate outlet; and a cooling tower fluidly connected tothe liquid desiccant outlet of the flash drum and the condenser, thecooling tower including a water stripper having a collector member, anda heat exchanger arranged below the water stripper, the collector memberbeing configured and disposed to receive water laden liquid desiccantand the heat exchanger being configured and disposed to receive make-upwater from the condenser.
 2. The water recovery system according toclaim 1, further comprising: a heat exchanger fluidly connected betweenthe desiccant outlet of the flash drum and the water stripper, the heatexchanger being configured and disposed to lower a temperature of liquiddesiccant flowing from the flash drum to the water stripper.
 3. Thewater recovery system according to claim 1, wherein the first circuitportion is fluidly isolated from the second circuit portion in theintercooler.
 4. The water recovery system according to claim 1, furthercomprising: a desiccant spray member arranged in the water stripper, thedesiccant spray member being fluidly coupled to the liquid desiccantoutlet of the flash drum.
 5. The water recovery system according toclaim 1, further comprising: a water spray member arranged in the waterstripper, the water spray member being fluidly coupled to the condensateoutlet of the condenser.
 6. The water recovery system according to claim5, wherein the water spray member directs the make-up water onto theheat exchanger.
 7. The water recovery system according to claim 1,wherein the collector member is fluidly connected to the first circuitportion.
 8. The water recovery system according to claim 1, wherein theheat exchanger is fluidly connected to the second circuit portion.
 9. Aturbomachine system comprising: a first turbomachine section includingan extraction outlet; a second turbomachine section including anextraction inlet fluidly connected to the extraction outlet of the firstturbomachine section; and a water recovery system operatively connectedto the turbomachine system, the water recovery system comprising: anintercooler member including a first circuit portion and a secondcircuit portion, the first circuit portion being configured and disposedto receive a liquid desiccant and the second circuit portion beingconfigured and disposed to receive coolant, the intercooler member beingconfigured and disposed to remove heat from an extraction fluid passingfrom the extraction outlet; a flash drum including an inlet fluidlyconnected to the first circuit portion, a vapor outlet and a liquiddesiccant outlet; a condenser fluidly coupled to the vapor outlet of theflash drum; and a cooling tower fluidly connected to the liquiddesiccant outlet of the flash drum and the condenser, the cooling towerincluding a water stripper having a collector member, and a heatexchange member arranged below the water stripper, the collector memberbeing configured and disposed to receive water laden liquid desiccantand the heat exchanger being configured and disposed to receive waterfrom the condenser.
 10. The turbomachine system according to claim 9,further comprising: a heat exchanger fluidly connected between theliquid desiccant outlet of the flash drum and the water stripper, theheat exchanger being configured and disposed to lower a temperature ofliquid desiccant flowing from the flash drum to the water stripper. 11.The turbomachine system according to claim 9, wherein the first circuitportion is fluidly isolated from the second circuit portion in theintercooler.
 12. The turbomachine system according to claim 9, furthercomprising: a desiccant spray member arranged in the water stripper, thedesiccant spray member being fluidly coupled to the liquid desiccantoutlet of the flash drum.
 13. The turbomachine system according to claim9, further comprising: a water spray member arranged in the waterstripper, the water spray member being fluidly coupled to the vaporoutlet of the flash drum.
 14. The turbomachine system according to claim9, wherein the collector member is fluidly connected to the firstcircuit portion.
 15. The turbomachine system according to claim 9,wherein the heat exchanger is fluidly connected to the second circuitportion.
 16. A method of extracting water from vapor emitted by acooling tower, the method comprising: passing a water laden liquiddesiccant though an intercooler; absorbing heat into the water ladenliquid desiccant forming a heat laden liquid desiccant; directing theheat laden liquid desiccant through a flash drum; extracting water vaporfrom the heat laden liquid desiccant in the flash drum forming asubstantially water free liquid desiccant; introducing the substantiallywater free liquid desiccant into wet air in the cooling tower; absorbingwater from the wet air into the substantially water free liquiddesiccant forming a water laden liquid desiccant; and passing the waterladen liquid desiccant back into the intercooler.
 17. The method ofclaim 16, further comprising: collecting the water laden liquiddesiccant in a collector arranged in the water stripper portion of thecooling tower.
 18. The method of claim 16, wherein introducing thesubstantially water free liquid desiccant into the wet air comprisesspraying the substantially water free liquid desiccant into the wet air.19. The method of claim 16, further comprising: passing the water vaporfrom the flash drum to a condenser to form liquid water.
 20. The methodof claim 19, further comprising: spraying the liquid water onto a heatexchanger in the cooling tower.